(1) Field of the Invention
This invention relates to a proces for the exposure of a semiconductor wafer, which is suitable for practice in the fabrication process of a semiconductor devices.
(2) Description of the Prior Art
The wavelength of light employed for the exposure of semiconductor wafers in the early years around 1965 was approximately 436 nm as typified by light radiated from a global supervoltage mercury vapor lamp which may also be called a short arc lamp. As time went on toward 1970 and further, the integration of IC devices proceeded significantly. It is recently required to effect exposure at a resolution as high as 1 .mu.m or even higher. Reflecting this, light of wavelengths ranging from 200 nm to 250 nm have now found utility in the exposure of semiconductor wafers (see, KIRA U.S. Pat. No. 5,190,786 and Japanese Patent Laid-Open No. 108478/1979).
It has however been known that as the wavelength of exposing light becomes shorter, more and more limitations are imposed on optical materials usable in an optical system and the exposing apparatus becomes more expensive. For these limitations, exposure of semiconductor wafers is still conducted using light of wavelengths ranging from 400 nm to 450 nm, although it is not expected to achieve any resolution as high as 1 .mu.m or even higher from the use of such light. Conventional global supervoltage mercury vapor lamps have however been pointed out to involve such drawbacks that they do not permit any further reduction of the effective pulse width at half maximum in their spectra and they are also susceptible to breakdown.